I still say Ultron would be best for this. He could be uploaded with the complete files for all the heroes. Knows every strength and weakness and the genius to manipulate them properly. A Scalpel.

Ant Man will have already been made if they want to stick to the comics more rather than have Stark build him. It also makes since that there are some major breakthroughs going on as we experiment and reverse engineer the captured alien tech.

That could work, too. I *do* think Hank and Janet will be available for Avengers 2, since filming will have wrapped on Ant-Man before TA2 starts shooting.